BSM_NH2 Transformation Coefficients

Attached are the BSM_NH2 Transformation Coefficients generated in December 2018. Thay are attached as a .ini file that can be opened with a text editor. This .ini file, after deleting the _.txt extension, can be loaded directly into Transform Applier.

BSM_NH2 is using the ZWO ASI-183mm-cool-pro camera. This is a 12-bit CMOS system, but used in a 2x2 binning mode which essentially gives 14-bit precision. ZWO's largest filter wheel has 8 positions, so we opted to remove the Rc filter and use SR (Sloan r) when R-band photometry was needed. That is why Ken shows transformation coefficients using SR that are larger than what you normally see for the typical Astrodon Rc filter.

The full BSM_NH2 filter set is B,V,Ic,u,g,r,i,z_s. It lost the Rc filter and the SA200 diffraction grating from the original BSM_NH filter set. It has a wide spectral range coverage from the Sloan set, part of the ongoing testing of the capabilities of these CMOS cameras. So far, I'm pleased with what I see.

We're waiting for MaximDL to implement a real-time stacking option, at which point we'll be able to go far brighter than the original BSM, and also be able to stack 4 images/filter before saving to obtain 16-bit precision on other fields.

If things work as they are described, we should be able to do everything, including Sirius. The big problem is scintillation. For Sirius, the exposures are about 0.01sec, and you need to coadd 1000 such exposures to reduce scintillation. For obvious reasons, you want to do this stacking in real time and just write the result to disk. If we can accomplish this, we won't even need to defocus.

Yes, Sirius is an exception. In order to image it, you have to seriously subframe, and so there would be little chance for a nearby star to use as a comparison. So for it, you'd have to work in the PEP mode, using a comp star a degree or more away.

For fainter stars, say mag 0 like Vega, you can image full frame, and so can use comp stars as faint as mag 6 or 7 since you are stacking ~20 seconds worth of exposures.

Attached are the BSM_NH2 Transformation Coefficients generated in May 2019. Thay are attached as a .ini file that can be opened with a text editor. This .ini file, after deleting the _.txt extension, can be loaded directly into Transform Applier.